Prosecutors will seek the death penalty for five other men arrested with him, police said on Tuesday. The six will be formally charged in court on Thursday on accusations that they kidnapped, gang-raped and murdered the 23-year-old woman in New Delhi on December 16, police spokesman Rajan Bhagat said.

Media reports said some 30 witnesses have been gathered, and the charges have been detailed in a document running to more than 1,000 pages.

Outraged Indians have been demanding the death penalty for the six men, holding demonstrations almost every day since the rape. Murder is punishable by death and rape by life imprisonment. But juveniles - those under the age of 18 - cannot be prosecuted for murder.

Another police officer said a bone test is being carried out to determine if the youngest suspect is indeed a juvenile. If the test determines he is 18 or older he will be treated as an adult, said the officer.

The brutality of the case has made Indians confront the reality that sexual violence is deeply entrenched in the society. Women face daily harassment, from catcalls on streets and groping in buses to rapes. Often police refuse to accept complaints by female victims and even accuse them of inviting unwanted male attention by dressing provocatively. Families also dissuade victims from coming forward in the belief that it will ruin their reputations.

Activists hope the savage assault on the woman, a physiotherapy student, will shake off the taboo and make authorities take such cases more seriously.

The woman and a male companion were attacked when they boarded a bus in southern New Delhi to go home. The six men, including the bus driver, allegedly took turns to rape her and beat her with an iron bar which they also inserted in her body, causing severe injuries to her organs.

The woman, who has not been identified, was airlifted to Singapore for emergency treatment but died on Saturday. She was cremated in New Delhi on Sunday, and her ashes were to be submerged in the River Ganges near her hometown in the northern Uttar Pradesh state in accordance with Hindu custom.

Protesters and politicians from across the spectrum called for a special session of Parliament to pass new laws to increase punishments for rapists - including possible chemical castration - and to set up fast-track courts to deal with rape cases within 90 days.